The present invention relates to an automatic focusing control method for microscope, more particularly to such a method suitable for use in an automatic cell differentiation apparatus based on a pattern recognition using a microscope.
In the conventional automatic focusing control for a microscope, importance was attached to an accurate and rapid automatic focusing for a certain point in a view field of the microscope. Prior art examples of the automatic focusing control for microscope are disclosed by JP-A No. 59-94711 and JP-A No. 59-100406. However, in spite of the fact that in the case of using an objective lens of high magnification (for example, 100 magnifications) a focal depth of the lens becomes so shallow as about 0.2 .mu.m, any correction for the displacement of a focal point resulting from a mechanical distortion of a movable stage of the microscope in upward and downward directions associated with the movement of the stage was not taken into consideration. Namely, no account was taken of an automatic focusing control for a blurred focus resulting from a change in relative distance between the objective lens and the microscope stage when the microscope stage is driven. As a result, the prior art involves a problem that a long time is required for the automatic focusing or the automatic focusing cannot be performed in an extreme case.